Dopamine and Reward Prediction Error Generalizability

It has been established that learning relies primarily on the brain’s ability to compare expectations with outcomes. Depending on the results, the brain adjusts future behavior based on what it considers worth repeating. Dopamine has previously been associated with reward and pleasure. Newer research established, however, that its primary function was to encode reward prediction error (RPE), the difference between expected and actual outcomes. This paper presents a literature review addressing the question: How do dopamine neurons represent learning signals for diverse behaviors, and to what extent is reward prediction error maintained and adapted across different contexts? Firstly, the paper analyzes foundational experimental papers that have enabled the scientific understanding of RPE as a computational principle and of dopamine signaling’s role in reward-based learning. Secondly, the paper presents evidence of RPE’s generalizability beyond external reward by reporting an experiment on songbirds. Thirdly, the paper reviews studies on courtship and maternal behavior, thereby showing that the dopaminergic system is adaptable, prioritizing social outcomes while maintaining the prediction error framework. Fourthly, an analysis of synaptic plasticity - the brain's ability to strengthen or weaken connections between neurons - is conducted. This explains the drive for learning and behavioral change: dopamine-dependent prediction-error evaluation. Finally, an analysis of the pathological consequences of deficiency in Parkinson's and dopamine excess in addiction is conducted, respectively. As a whole, the analysis and synthesis of the experiment's findings strongly suggest a universal mechanism: reward prediction error. Furthermore, the experiments demonstrate RPE’s flexibility in response to the agent's current goals. Additionally, RPE extends beyond reward acquisition to encompass performance evaluation, social behavior, parenting, and neurological conditions across species.